1. Field of the Invention
The present invention relates to the preparation of aromatic or aliphatic nitriles, and, more especially, to the preparation of nitriles having the general formula: EQU Ar--A--CN (I)
wherein Ar represents a substituted or unsubstituted benzene radical and A represents a direct chemical bond or a hydrocarbon radical having from 1 to 6 carbon atoms, from formamides or formanilides having the general formula: EQU Ar--A--NHCHO (II)
or amides having the general formula: EQU Ar--A--CONH.sub.2 (III)
wherein Ar and A are as above defined.
2. Description of the Prior Art
It is known to this art, from French Pat. No. 1,250,165, to prepare nitriles from compounds of the aforesaid type (II) by reactively contacting the same, at a temperature ranging from 460.degree. to 560.degree. C., and in the gaseous phase, with a catalyst comprising active silicic acid or silicates containing a metal oxide.
Nonetheless, carrying out the subject reaction with catalysts of the type described in the aforecited French patent evidences that the selectivity realized is not sufficient for optimal industrial utilization of the process. Furthermore, when nitriles of the Formula I are desired, wherein the radical Ar bears a fluorine substituent, the process promotes the formation of heavy by-products which shortens the life of the catalyst by encrusting its surface, and defluorination reactions too are observed, resulting in compounds which are extremely difficult to separate from the desired product.